This invention relates to a drive mechanism for a wheeled vehicle wherein the driving wheel of such vehicle may be driven in either rotational direction and wherein force applied in the opposite direction to which the wheel is traveling will effect a braking action thereto. Such driving mechanisms have particular utility for transmitting a driving force from a pedal operated vehicle such as a bicycle or tricycle to its driven wheel so that the vehicle can be moved in either direction. With such vehicles it is also desirable that they be able to coast, that is, move without the application of force to the drive wheel, and to further enable the driving wheel to be braked as by the application of force to the driving wheel in a direction opposite to that in which it is traveling.
Devices of this general type are known and include those devices disclosed in U.S. Pat. No. 2,246,191 to Schmitz issued June 17, 1941 and U.S. Pat. No. 3,650,363 to Cristie issued Mar. 21, 1972. The device disclosed in the Schmitz patent includes a driving wheel hub having an axle rotatably supported therethrough. The axle is in turn provided with a threaded portion adapted to receive a driving member 15 comprising a pair of interfitting collars 17, 19 so that rotation of the axle will drive the collars as a unit side to side within the hub. The hub further includes a shoulder portion 27 on one side and a chamfered portion 31 on the other side of the hub with which portions of the collar are adapted to engage in frictional driving relationship so that rotational force imparted to the axle in either direction will impart such force to the driving hub. The driving element made up of the cooperating collar members is prevented from rotating as a unit with the threaded portion of the axle by means of spring clip finger portions 20 which extend in slidable engagement with the surface of the driver member 15.
A similar device in the form of a clutch mechanism is disclosed in the above-identified Cristie patent in which a clutch cone 62 moves axially within a sleeve 56 upon an axle 46 between an engaged driving position and a disengaged position. In the disengaged clutch position, it is possible to simultaneously provide a braking action to the forward movement of the wheel supported by the sleeve or hub 56. This action is accomplished by a screw upon which the clutch cone is mounted for axial movement within the sleeve upon rotation of the axle.
The above citations and discussion of those patents believed pertinent constitute applicant's Prior Art Statement and in that regard copies of the above-indicated patents are enclosed with the subject application.
Although the prior art devices are useful for the purposes indicated, it would be desirable if a more simple and economic means could be devised to permit traversing motion of the driver of such a driving mechanism while preventing it from rotating around the axle without resorting to arrangements such as the spring fingers of Schmitz which are subject to wear and breakage and the complex and accordingly expensive mechanisms of Cristie. It is accordingly a primary object of the present invention to provide a drive mechanism in which an axially movable threadedly mounted driver member is restrained from concurrent rotation with the axle by means of its configuration rather than by means of outside or added elements and which accordingly is less complex and less expensive than known prior art devices.
A further object of the present invention is the provision of a device of the immediately aforementioned type in which the axially movable driver element is eccentrically weighted in such a manner that it resists concurrent rotation with the axle upon which it is threadedly mounted.
Another object is the provision of means which cause the driver to more readily break away from driving engagement when the rotational direction of the axle is reversed.
These and other objects of the present invention are accomplished by the provision of a drive mechanism comprising a hub, said hub having contact faces at opposite inner ends thereof, an axle extending through said hub and supported thereby for rotation in opposite directions, said axle having a threaded screw portion disposed within said hub and an eccentrically weighted driver threadably mounted within said hub upon said screw portion for non-rotational longitudinal movement therewith whereby rotation of said axle in opposite directions traverses said driver from side to side into driving contact with said opposite faces of said hub wherby driving force in opposite directions is imparted to said hub.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawing.